HR: 0800h
AN: SA11A-0297    [Abstracts]
TI: Emission of ELF/VLF Waves by a Modulated Electrojet upwards into the Ionosphere and into the Earth-Ionosphere Waveguide
AU: * Lehtinen, N G
EM: nleht@stanford.edu
AF: Stanford University, 350 Serra Mall, Stanford, CA 94305, United States
AU: Inan, U S
EM: inan@stanford.edu
AF: Stanford University, 350 Serra Mall, Stanford, CA 94305, United States
AB: The modulation of the auroral electrojet by a ground-based ionosphere heating facility is calculated by solving a kinetic equation for electron distribution function. The resulting current is used to calculate the emission of ELF/VLF waves both into ionosphere and into the Earth-ionosphere waveguide. For this purpose, we developed a finite element method of calculation of electromagnetic field in a horizontally-stratified ionosphere filled with magnetized plasma, with arbitrary harmonically-varying current distribution and the direction of geomagnetic field. This method is proven to be stable against the loss of precision due to "swamping" of useful modes by evanescent waves. The electromagnetic field is calculated both in the Earth-Ionosphere waveguide (at arbitrary horizontal distance and direction) and in the ionosphere (as a whistler mode). The presented method requires less computational resources than traditional FDFD and FDTD methods. The calculated values are compared to ground and satellite observations of electrojet emissions from modulation by existing ionosphere heating facilities. In particular, we find that the emission of the whistler waves upward into the ionosphere is contained in a relatively narrow channel, even in the absence of ducting, due to a substantial horizontal size of the emitting region. We discuss the difference in the treatment of the heating of free electron by using the kinetic approach and the approach assuming a thermal (Maxwellian) distribution of electrons.
DE: 2403 Active experiments
SC: SPA-Aeronomy [SA]
MN: 2007 Fall Meeting